Pressure reducing devices

ABSTRACT

A pressure reducing device comprises an inlet for high pressure gas, an outlet for low pressure gas and a path therebetween for flow of gas from inlet to outlet. The path includes at least one porous baffle having a relatively coarse pore inner portion disposed in an inner zone of said path and a relatively fine pore outer portion in an outer zone of said path. Porous materials that may be used include layers of gauze, expanded metal, sintered metal, ceramic foams and plastics foams such as rigidified foams.

United States Patent King [451 July 18,1972

[73] Assigne'e: Dunlop Holdings Limited, London, En-

gland [22] Filed: July 8, 1970 [21] Appl.No.: 53,162

[30] I Foreign Application Priority Data Jan. 15, 1970 Great Britain..2,001/70 [52] U.S.Cl ..l38/42, 137/6253, 138/40, 138/44 51 Int. Cl,....Fl5d 1/02 [58] Field of Search 138/42, 43, 44, 40, 41; Yl37/112,517, 625.3

[56] References Cited UNITED STATES PATENTS 3,042,079 7/1962 Swift..138/42 Behlen ..138/42 X 1,947,586 2/1934 Fletcher 138/42 2,304,68912/1942 Hemson 1 38/42 2,090,719. .8/1937 Alt ...l38/44 X 2,815,88912/1957 Stetz..... ...l38/42 X 2,327,195 8/1943 Koslry ..138/43 PrimaryExaminer-Herbert F. Ross Attorney-Stevens, Davis, Miller & MosherABSTRACT A pressure reducing device comprises an inlet for high pressuregas, an outlet for low pressure gas and -a path therebetween for flow ofgas from inlet to outlet. The path includes at least one porous bafflehaving a relatively coarse pore inner portion disposed in an inner zoneof said path and a relatively fine pore outer portion in an outer zoneof said path. Porous materials that may be used include layers of gauze,expanded metal, sintered metal, ceramic foams and plastics foams such asrigiditied foams.

16 Claims, 3 Drawing Figures PATENTEDJUL18|972 3677300 SHEET 1 BF 2FICLI PATENTEU JUL! 8 I972 SHEET 2 OF 2 This invention relates topressure reducing devices.

It is frequently necessary to reduce a high pressure stream of gas to alow pressure stream. Such a requirement often occurs in high pressuredistribution of gases where the pressure is required to be reducedbefore transmission to the point of use. Conventionally, the reductionin pressure is achieved by passing the high pressure gas through a ducthaving a relatively large cross-sectional area. This procedure tends tocreate a high level of noise which can present a serious problem, forexample where large quantities of gas are depressurized in urban areas.

According to the present invention a pressure reducing device comprisesan inlet for high pressure gas, an outlet for low pressure gas and apath therebetween for flow of gas from inlet to outlet. The pathincludes at least one porous baffle having a relatively coarse poreinner portion disposed in an inner zone of said path and a relativelyfine pore outer portion in an outer zone of said path.

The inner and outer portions of the baffle according to this inventionmay be integral or independent. When independent the portions may be incontact with one another or spaced apart.

In general, the arrangment of the porous baffles should be such as topermit expansion of the gas while reducing to a minimum the turbulenceproduced by the expansion.

In a preferred embodiment of the invention the outer portion may beformed by a female cone of porous material having an axial bore. In analternative embodiment the outer portion may be formed by a series ofco-axial annular discs of a porous material, whose internal diametersincrease from inlet to outlet. These discs may or may not be contiguous.Advantageously, the inner portion is conical or part-spherical.

The outer portion may be uniform throughout or it may have one or morecavities therein. These cavities may be enclosed at least in part byporous material. Thus, for example the pressure reducing device maycomprise an outer portion formed from a female cone of porous material,wherein, the body of the female cone is hollow, thereby forming a cavitywhich is totally enclosed by porous material.

Porous materials that may be used in the present invention include:layers of gauze, expanded metal, sintered metal,

ceremic foams and plastics foams such as rigidified foams.

The baffles according to this invention may be housed in a tube ofsuitable material positioned between the high pressure inlet and the lowpressure outlet, in which case the baffles are sealed in the tube toprevent gas from by-passing them. Alternatively, the baffles may becoated on their external surfaces with a suitable material, i.e.laminated aluminium foil/epoxy skin or a glass reinforced plastics skin,these units then being placed between the high pressure inlet and lowpressure outlet.

The baffles may be used alone or in conjunction with an additionalmechanical reducing valve and/or with other types of baffle.

A preferred embodiment of the invention is hereinafter described withreference to the accompanying drawing in which FIG. 1 shows adiagrammatic cross section of a first embodiment;

FIG. 2 is a cross section of an alternate embodimenthaving contiguousannular discs and a spaced apart inner section, and FIG. 3 is a furtherembodiment having spaced apart discs.

The preferred embodiment shown in FIG. 1 comprises a cylindrical inletand a coaxial cylindrical outlet 1 1 having a substantially largerdiameter than the inlet 10.

Disposed between the inlet 10 and outlet 11 is a porous baffle made upof independent inner and outer portions. The outer portion 30 is in theform of a female cone, of relatively fine pore foam metal, which has acentral bore 32. The inner portion 31 is in the form of a male cone ofrelatively coarse pore foam metal, and is located in the central bore 32in contact with the outer portion 30.

The whole arrangement is sealed in tube 33 by a ring of 55 inch thick,pore/inch polyurethane foam (not shown) which is adhered to the pressurereducing device and is compressed when the device is fitted in the tube.

A pressure reducing device of the type described above was constructedin which: the male cone which forms the inner portion has base diameter76 mm and height 102 mm-and is made from foam metal having 8 pores perinch; the female cone which forms the outer portion has diameter 76 mmand an overall length of 127 mm, and is made from foam metal having 80pores per inch.

The noise level produced by a stream of air in the above pressurereducing device was measured using air velocity of 7.4 m/sec. In theabsence of the diaphram the sound level was measured as 96 dB, whereasthe arrangement described above produced a sound level of 79 dB and alsosilenced the high pitched whistle which was characteristic of the emptypipe.

When the above device was used together with three foam metal discs 76mm in diameter and 13 mm thick made from 80 pores per inch foam, thesediscs being sealed in the outlet pipe 77 mm, 191 mm and 305 mmrespectively, after the base of the male cone, the noise level wasreduced to 75 dB. However, the air velocity was also reduced to 7.1mm/sec.

In the embodiment shown in FIG. 2, the tube 37 contains a plurality ofcontiguous annular discs 35 of increasing internal diameter as an outerportion and an inner portion 34 which is spaced therefrom. In theembodiment shown in FIG. 3, the annular discs 35 are separated by spaces36, the inner portion 31 being similar to that shown in FIG. 1. In anyof the embidiments, the baffles may be coated on their external surfaceswith a material such as a laminate such as aluminum foil and a plasticsmaterial or a glass reinforced plastics material.

Having now described my invention what I claim is:

l. A pressure reducing device comprises an inlet for high pressure gas,an outlet for low pressure gas and a path therebetween for flow of gasfrom inlet to outlet, said path including at least one porous bafilehaving at least two portions, the first being a relatively coarse poreinner portion disposed in an inner zone of said path and the other beinga relatively fine pore outer portion in an outer zone of said path.

2. A pressure reducing device according to claim 1 in which the innerand outer portions are in contact with one another.

3. A pressure reducing device according to claim 2 in which the innerand outer portions are integral.

4. A pressure reducing device according to claim 1 in which the innerand outer portions are spaced apart.

5. A pressure reducing device according to claim 1 in which the outerportion is formed by a female cone of porous material, having an axialbore.

' 6. A pressure reducing device according to claim 1 in which the outerportion is formed by a series of coaxial annular discs of increasinginternal diameter.

7. A pressure reducing device according to claim 6 in which the discsare contiguous with one another.

8. A pressure reducing device according to claim 6 in which the discsare spaced apart.

9. A pressure reducing device according to claim 1 in which the outerportion has at least one cavity which is enclosed at least in part byporous material.

10. A pressure reducing device according to claim 1 in which the innerportion is thicker in its central region than in its outer region.

11. A pressure reducing device according to claim 1 in which the innerportion is at least partly curved.

12. A pressure reducing device according to claim 1 in which each baffleis disposed within at least one duct.

13. A pressure reducing device according to claim I in which the bafflesare coated on their external surfaces.

14. A pressure reducing device according to claim 13 in which thecoating is a laminate of aluminum foil and a plastics material.

15. The device of claim 1 in which the relatively coarse inner portionhas less than 10 pores per inch and the relatively fine outer portionhas at least 50 pores per inch.

16. The device of claim 1 in which the relatively coarse inner portionhas about 8 pores per inch and the relatively fine outer portion hasabout 80 pores per inch.

1. A pressure reducing device comprises an inlet for high pressure gas,an outlet for low pressure gas and a path therebetween for flow of gasfrom inlet to outlet, said path including at least one porous bafflehaving at least two portions, the first being a relatively coarse poreinner portion disposed in an inner zone of said path and the other beinga relatively fine pore outer portion in an outer zone of said path.
 2. Apressure reducing device according to claim 1 in which the inner andouter portions are in contact with one another.
 3. A pressure reducingdevice according to claim 2 in which the inner and outer portions areintegral.
 4. A pressure reducing device according to claim 1 in whichthe inner and outer portions are spaced apart.
 5. A pressure reducingdevice accorDing to claim 1 in which the outer portion is formed by afemale cone of porous material, having an axial bore.
 6. A pressurereducing device according to claim 1 in which the outer portion isformed by a series of coaxial annular discs of increasing internaldiameter.
 7. A pressure reducing device according to claim 6 in whichthe discs are contiguous with one another.
 8. A pressure reducing deviceaccording to claim 6 in which the discs are spaced apart.
 9. A pressurereducing device according to claim 1 in which the outer portion has atleast one cavity which is enclosed at least in part by porous material.10. A pressure reducing device according to claim 1 in which the innerportion is thicker in its central region than in its outer region.
 11. Apressure reducing device according to claim 1 in which the inner portionis at least partly curved.
 12. A pressure reducing device according toclaim 1 in which each baffle is disposed within at least one duct.
 13. Apressure reducing device according to claim 1 in which the baffles arecoated on their external surfaces.
 14. A pressure reducing deviceaccording to claim 13 in which the coating is a laminate of aluminumfoil and a plastics material.
 15. The device of claim 1 in which therelatively coarse inner portion has less than 10 pores per inch and therelatively fine outer portion has at least 50 pores per inch.
 16. Thedevice of claim 1 in which the relatively coarse inner portion has about8 pores per inch and the relatively fine outer portion has about 80pores per inch.